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-rw-r--r--ipc/sem.c32
1 files changed, 21 insertions, 11 deletions
diff --git a/ipc/sem.c b/ipc/sem.c
index 51352e1bfff9..41088899783d 100644
--- a/ipc/sem.c
+++ b/ipc/sem.c
@@ -154,12 +154,15 @@ static int sysvipc_sem_proc_show(struct seq_file *s, void *it);
#define SEMOPM_FAST 64 /* ~ 372 bytes on stack */
/*
- * linked list protection:
+ * Locking:
* sem_undo.id_next,
+ * sem_array.complex_count,
* sem_array.pending{_alter,_cont},
- * sem_array.sem_undo: sem_lock() for read/write
+ * sem_array.sem_undo: global sem_lock() for read/write
* sem_undo.proc_next: only "current" is allowed to read/write that field.
*
+ * sem_array.sem_base[i].pending_{const,alter}:
+ * global or semaphore sem_lock() for read/write
*/
#define sc_semmsl sem_ctls[0]
@@ -536,12 +539,19 @@ SYSCALL_DEFINE3(semget, key_t, key, int, nsems, int, semflg)
return ipcget(ns, &sem_ids(ns), &sem_ops, &sem_params);
}
-/*
- * Determine whether a sequence of semaphore operations would succeed
- * all at once. Return 0 if yes, 1 if need to sleep, else return error code.
+/** perform_atomic_semop - Perform (if possible) a semaphore operation
+ * @sma: semaphore array
+ * @sops: array with operations that should be checked
+ * @nsems: number of sops
+ * @un: undo array
+ * @pid: pid that did the change
+ *
+ * Returns 0 if the operation was possible.
+ * Returns 1 if the operation is impossible, the caller must sleep.
+ * Negative values are error codes.
*/
-static int try_atomic_semop (struct sem_array * sma, struct sembuf * sops,
+static int perform_atomic_semop(struct sem_array *sma, struct sembuf *sops,
int nsops, struct sem_undo *un, int pid)
{
int result, sem_op;
@@ -724,8 +734,8 @@ static int wake_const_ops(struct sem_array *sma, int semnum,
q = container_of(walk, struct sem_queue, list);
walk = walk->next;
- error = try_atomic_semop(sma, q->sops, q->nsops,
- q->undo, q->pid);
+ error = perform_atomic_semop(sma, q->sops, q->nsops,
+ q->undo, q->pid);
if (error <= 0) {
/* operation completed, remove from queue & wakeup */
@@ -838,7 +848,7 @@ again:
if (semnum != -1 && sma->sem_base[semnum].semval == 0)
break;
- error = try_atomic_semop(sma, q->sops, q->nsops,
+ error = perform_atomic_semop(sma, q->sops, q->nsops,
q->undo, q->pid);
/* Does q->sleeper still need to sleep? */
@@ -1686,7 +1696,6 @@ static int get_queue_result(struct sem_queue *q)
return error;
}
-
SYSCALL_DEFINE4(semtimedop, int, semid, struct sembuf __user *, tsops,
unsigned, nsops, const struct timespec __user *, timeout)
{
@@ -1784,7 +1793,8 @@ SYSCALL_DEFINE4(semtimedop, int, semid, struct sembuf __user *, tsops,
if (un && un->semid == -1)
goto out_unlock_free;
- error = try_atomic_semop (sma, sops, nsops, un, task_tgid_vnr(current));
+ error = perform_atomic_semop(sma, sops, nsops, un,
+ task_tgid_vnr(current));
if (error <= 0) {
if (alter && error == 0)
do_smart_update(sma, sops, nsops, 1, &tasks);

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